Spotlights and floodlights often must be aimed along specific axes in order to fit an overall lighting scheme. Such aiming is generally laborious and time consuming. If the lights are moved for relamping or cleaning, they must be reset thereafter to the original aim and it is desirable to do so without having to repeat the original laborious procedure. The luminaire trunnion degree marker and reset stop is used for this purpose.
By way of example, an outdoor sports stadium may be lit by several hundred floodlight type luminaires which are clustered in light towers located on top of the grandstand surrounding the field. Each fixture must be aimed at a particular designated point on the field for most efficient use in achieving the desired lighting pattern on the playing surface. Blueprints are prepared indicating for each fixture its coordinating point on the field. The entire playing surface is walked off along quadrant lines a suitable distance apart, say 30'. At the quadrant line intersections, a white paper plate with the corresponding fixture's blueprint number is nailed to the ground. An electrician in the light tower then contacts by radio an associate standing amidst the sea of paper plates in order to make the correlation of a given fixture to its plate. The fixture is equipped with a simple sight or aiming device through which the electrician can aim at the designated paper plate. The electrician then tightens the trunnion bolts to lock the floodlight in its aimed attitude and this procedure is repeated for every floodlight.
In the foregoing example and in many other applications, the floodlights are aimed down, often overhanging a parapet or ledge, and it would be very difficult and possibly dangerous to attempt to service the fixture in that attitude. The common practice for relamping is to loosen the two trunnion bolts and tilt the fixture back. The electrician can then open the lens or cover and conveniently replace the lamp by reaching down into the fixture. After relamping it should be possible to simply and accurately reset the floodlight to its original aim, and the function of the luminaire trunnion degree marker and reset stop is to permit this.